Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
Keep in mind that octane ratings (recently AKI indexes which is an average octane) vary across the country with various areas having lower octane fuel (often higher altitude with old agreements about what is appropriate in the area) and some with higher octane available. Also keep in mind that fuel changes with seasons in many areas to control volatility in temperature swings).
Unleaded gasoline across the country today will vary from 85 octane to 94 octane, most with 10% ethanol but some without.
Your best bet 99% of the time is to simply use the octane rating (or higher) recommended by the auto manufacturer.
Not exactly correct. One of the variables used in octane testing and calculation relates to altitude. So, the SAME EXACT fuel that is rated at 87 octane at sea-level will only get an 85 rating at, say 5,000 feet elevation. That is why, in my home state of Colorado (thw whole state above 3,300 feet elevation), regular gasoline is almost always 85 octane-rated, not because the fuel is any different than what is sold somewhere else in the country and rated at 87 octane there.
The higher the octane rating, the slower the fuel burns. Octane rating
Gasoline with a higher heating value (energy content) provides better fuel economy. Traditionally, premium gasoline has had a slightly higher heating value than regular, and, thus, provides slightly better fuel economy, but it is difficult to detect in normal driving.There can be even larger differences in heating value between batches of gasoline from the same refinery, between summer and winter volatility classes, or between brands of gasoline from different refineries because of compositional differences.
Octane number is a measurement of fuel’s resistance to engine knock. Engine knock is an abnormal combustion associated with using gasoline with too low of an octane number. Ordinarily, your vehicle will not benefit from using a higher octane than is recommended in the owner’s manual.
The correct name for the (RON+MON)/2 formula is the "antiknock index",
If you use a fuel with an octane rating below the requirement of the engine, the management system may move the engine settings into an area of less efficient combustion, resulting in reduced power and reduced fuel economy. You will be losing both money and driveability. If you use a fuel with an octane rating higher than what the engine can use, you are just wasting money by paying for octane that you can not utilise. Forget the stories about higher octanes having superior additive packages - they do not. If your vehicle does not have a knock sensor, then using an octane significantly below the requirement means that the little men with hammers will gleefully pummel your engine to pieces.
Most people know that an increase in Compression Ratio will require an increase in fuel octane for the same engine design. Increasing the compression ratio increases the theoretical thermodynamic efficiency of an engine according to the standard equation
Efficiency = 1 - (1/compression ratio)^gamma-1
If you use a fuel with an octane rating below the requirement of the engine, the management system may move the engine settings into an area of less efficient combustion, resulting in reduced power and reduced fuel economy. You will be losing both money and driveability.
+1
If you use 87 in an engine that needs premium, you may encounter knock, which will be picked up by your engine's knock sensor, which in turn tells the ECM to pull timing in an attempt to rid the knock, which in turn costs you power. On top of that, the knock, which is really detonation, is hammering away on your engine's internals, leading it to a premature death.
Egine knock is pre-detonation. Which, simply put, means that the gasoline explodes during compression rather than at the peak of the compression cycle. Extreme knock can destroy your engine immediately, but it rarely does. More normal levels of knock can damage your engine, but we never saw it with older cars that had pre-ignitiion or "pinging" frequently. In fact from 1978 through 1988 I never wore out an engine except one in a Honda Cvcc (which was a breeze to rebuild), despite getting pre-ignition quite regularly.
Again premium octane gas does not burn hotters or better or with a greater explosion. It just does nor explode prematurely.
Back in the 1970s and 1980s it was not uncommon to get a tank of gas that would "ping" or knock like crazy. Sometimes our big Catalina would ping like mad and dog out when going up a big hill or when rapidly accelerating. I am not sure why. You could go back two days later and fill up from the same pump and it would be fine. Generally if you got a tank of bad gas, you just dumped a bottle of octane booster into the tank and it was fine (depending on which one you used, some of them did nothing and the pinging continued). Back then they did not always call it octane booster. They called it anti-knock or ping preventer and other silly names.
If your engine is constantly pinging, I hear you should start using mid-grade or premium even if the manual says to use Regular and it hasn't been pinging in the past.
If your engine is constantly pinging, I hear you should start using mid-grade or premium even if the manual says to use Regular and it hasn't been pinging in the past.
as far as I can remember we did nto have grades of gas back then. Just leaded and unleaded.
as far as I can remember we did nto have grades of gas back then. Just leaded and unleaded.
Huh? Back before unleaded gasoline, there was regular and premium (often called "ethyl"). In the late 1960's and early 1970's, Conoco experimented with selling four grades of gasoline at its pumps. When unleaded came along, many stations carried unleaded regular, leaded regular, and premium leaded for several years. The switch to carrying unleaded premium (and mid-grade unleaded) came after the sale of leaded gasoline was outlawed.
The question I have is does it really cost gas company more to refine the higher octane mixture? I'm willing to wager that if it does, it's only a few cents difference, not the 10 cent or 20 cents more a gallon they charge.
If your engine is constantly pinging, I hear you should start using mid-grade or premium even if the manual says to use Regular and it hasn't been pinging in the past.
If your made for regular gas engine starts pinging theres a problem happening , switching to a higher octane gas will probably cause the pinging to abate but the problem is still there.
Please register to post and access all features of our very popular forum. It is free and quick. Over $68,000 in prizes has already been given out to active posters on our forum. Additional giveaways are planned.
Detailed information about all U.S. cities, counties, and zip codes on our site: City-data.com.
Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
